Immobilized different amines on modified magnetic nanoparticles as catalyst for biodiesel production from soybean oil

Fe₃O₄ nanoparticles were modified with tetraethylorthosilicate (TEOS) and (3-chloropropyl)trimethoxysilane (CPTMS) followed by immobilization with different amines such as guanine, piperazine, methylamine, morpholine, aniline, ethylenediamine, 3-aminopropyltriethoxysilane, and melamine, designated as Fe₃O₄@SiO₂@CPTMS@amine (nanocatalyst). The prepared nanocatalysts were characterized by means of FTIR, XRD, VSM, SEM, and TEM. Trans-esterification reactions of soybean oil with methanol were then carried out in the presence of the Fe₃O₄@SiO₂@CPTMS@amine as a nanocatalyst. Optimization of the reaction parameters revealed that the fatty acid methyl esters (FAMEs or biodiesel) is obtained in 6–96% yields by using methanol to oil molar ratio of 36 in the presence of 6% of nanocatalysts containing melamine and guanine, respectively, at 160 °C within 3 h. The stability and reusability of the catalyst as well as the effect of reaction parameters on the FAME yield are described in this paper.     

Solubility of sildenafil citrate in propylene glycol + water mixtures at various temperatures

The solubility of sildenafil citrate (SC) in aqueous mixtures of propylene glycol (PG) was investigated. This study was carried out at different mass fractions of PG ranging from 0.1 to 0.9 at T = 293.2–313.2 K. The solubility of SC in the mixed solutions increased with increasing temperature and PG mass fraction.

The solubility values were correlated by two co-solvency models (Jouyban–Acree model and van’t Hoff–Jouyban–Acree model). The mean relative deviations (MRD) were 5.7% and 5.5%, respectively. Density of the SC-saturated solutions over the entire solvent composition and temperature range was also measured and the results correlated with the Jouyban–Acree model. Furthermore, the apparent thermodynamic properties, dissolution enthalpy, dissolution entropy and Gibbs free energy change of dissolution process of SC in all the mixed solvents were calculated according to van’t Hoff and Gibbs equations. Dissolution of SC in these mixed solvents is an endothermic process.     

Template-free synthesis of MnO2 nanowires with secondary flower like structure: Characterization and supercapacitor behavior studies

Manganese dioxide (MnO₂) nanowires with diameter about 30-70 nm is achieved via a two-step process: first, template-free cathodic electrodeposition from aqueous solution of Mn(NO₃)₂ on steel substrate and followed by heat treatment. The temperature-annealed sample was studied by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) methods and Fourier transform infrared (FT-IR) spectroscopy. The electrochemical performance of the MnO₂ sample was studied by cyclic voltammetry (CV) and chronopotentiometry in Na₂SO₄ solutions. The sample showed excellent supercapacitive behavior. The specific capacitance (SC) of 237 F g⁻¹ in a potential window of 0-0.9V was obtained at the scan rate of 2 mV s⁻¹. The SC calculated from the chronopotentiometry data is about 246 F g⁻¹. The SC was decreased by 16% after 1000 cycles.     

In vitro curcumin delivery and antibacterial activity of RuS2 and RuO2 nanoparticles loaded chitosan biopolymer

In this work, RuS₂ and RuO₂ nanoparticles loaded chitosan (Chitosan was extracted from Lobsters shells of Persian Gulf, IR. Iran) was prepared and characterized via FE‐SEM, EDS and FT‐IR analysis. FESEM showed the formation of spherical nanoparticles in size ranging of 20 to 100 mm. Subsequently, the role of these new materials as curcumin drug carrier and in vitro release of curcumin in simulated body fluid (SBF) solution (pH 7.4) were studied. RuS₂‐NPs‐CS than to RuO₂‐NPs‐CS showed higher drug loading efficiency (>91%) and rapid (<90 min) curcumin drug release in SBF solution. Also, antibacterial activity of RuS₂‐NPs‐CS and RuO₂‐NPs‐CS in presens and absence of Rosemary extracts against the gram negative bacteria Pseudomonas aeruginosa (PAO 1) was evaluated by detection of minimal inhibition concentration (MIC) and minimal bactericidal concentration (MBC). MIC of RuS₂‐NPs‐CS, RuO₂‐NPs‐CS and Rosemary extracts on Pseudomonas aeruginosa strains were found to be 50 mg/ml, 50 mg/ml and 1250 mg/ml, respectively. The synergistic effect of these materials for inhibition of PAO 1 growth showed that mixture of RuS₂‐NPs‐CS and Rosemary extracts has a better efficiency than to other mixture materials.     

Biosynthesis of Fe3O4-magnetic nanoparticles using clover leaf aqueous extract: Green synthesis of 1,3-benzoxazole derivatives

In this research, magnetic Fe₃O₄-NP nanoparticles were synthesized employing a green biosynthetic procedure by reduction of ferric chloride solution with clover leaf water extract. The nanoparticles prepared via this biosynthesis method can potentially be valuable for different purposes such as organic synthesis. In this research, 1,3-benzoxazole derivatives were generated via a multicomponent reaction of α-bromo ketones, isothiocyanate, and propiolate in the presence of a catalytic amount of bio-Fe₃O₄ MNPs and sodium hydride in water at 50°C in good yields. The catalyst was reused five times with a minor decrease in its catalytic activity.     

Synthesis and characterization of Si-Zr-Mo nanocomposite as a rapid and efficient catalyst for aromatization of Hantzsch 1,4-dihydropyridines

Nanocomposite of Silica-zirconia-molybdate designated as Si-Zr-Mo was prepared via the reaction of the in situ generated zirconium-tetra octanoxide [Zr(Oct)₄] through condensation of zirconium-tetra-n-butoxide and 1-octanol in a sol–gel method with sulfuric acid and tetraethylorthosilicate (TEOS) followed by grafting of MoO₄^2? on modified silico zirconia nanocomposite under reflux conditions. The prepared nanocomposite was characterized using inductively coupled plasma (ICP), N₂ sorption isotherms, transmission electron microscopy (TEM), and FT-IR spectroscopy. The as prepared nanocomposite had a surface area and pore dimension of 140 m²/g and 1.48 nm, respectively. The morphology of sulphated silico zirconia nanocomposite after immobilization MoO₄^2? has been changed from nanoparticles to nanaorods. It was found that the synthesized nanocomposite successfully catalyze the oxidative dehydrogenation of 1,4-dihydropyridines (1,4-DHPs) with 92–100% conversion and 80–100% selectivity toward the desired products.     

New method to posynomial geometric programming of trapezoidal fuzzy numbers

This paper presents a method for solving posynomial geometric programming with fuzzy coefficients. By utilizing comparison of fuzzy numbers with a method, the programming with fuzzy coefficients is reduced to the programming with constant coefficients. Then the programming with fuzzy coefficients can be solved by using a method for posynomial geometric programming. Finally, one comparative example is used to illustrate advantage of the new method.     

Synthesis and Characterization of Copper Ferrite Nanocrystals via Coprecipitation

Nanocrystalline CuFe₂O₄ powder was prepared by a coprecipitation method from iron chloride and copper chloride in the presence of octanoic acid (C₈H₁₆O₂) as surfactant. The as-prepared samples were characterized by XRD, TEM, SEM, FT-IR and VSM. SEM and TEM indicated that the particles were quasi spherical with the particle sizes in the range of 23±7?nm. The magnetic properties of the sample were measured by using a vibration sample magnetometer (VSM), which showed that the sample exhibited a typical ferromagnetic behavior at room temperature, while present finite coercivity of 245.5?Oe at 300?K.     

Solvent Effects on Tautomeric and Microscopic Protonation Constants of Glycine in Different Aqueous Solutions of Methanol and Ethanol

The acid-base equilibria of glycine have been studied in different aqueous solutions of methanol and ethanol (0?C45?% v/v) using a potentiometric method. In this study, the macro and micro protonation constants of the amino acid and its tautomeric constant have been determined at 25?°C and constant ionic strength (0.1 mol?dm^?3 NaClO₄). The protonation and the tautomeric constants of glycine in different binary mixtures were analyzed in terms of the Kamlet, Abboud and Taft (KAT) parameters. Single-parameter correlations of the constants versus ?? (hydrogen-bond donor acidity), ?? (hydrogen-bond acceptor basicity) and ?? ^? (dipolarity/polarizability) are poor in all solutions. Multi-parameter correlations show better results, but dual-parameter correlations represent significant improvements with regard to the single- and multi-parameter models. Linear correlation is observed when the experimental protonation constant values are plotted versus the calculated ones when the KAT parameters are considered. Finally, the results are discussed in terms of the effect of the solvent on protonation and tautomeric constants.